Document US2003/046921 describes a Hall-effect thruster with atmospheric gas as propellant. Such a thruster uses particles of the residual atmosphere in which it maneuvers to operate.
Hall-effect thrusters with atmospheric gas as the propellant are mainly used to propel observation satellites; these thrusters are particularly useful in low orbit.
At this altitude, the residual atmosphere slows the satellites, which limits their lifetime. Advantageously, Hall-effect thrusters with atmospheric gas as the propellant allow this drag to be compensated, which thus increases the lifetime of the satellites.
However, taking into account the atmospheric rarefaction with altitude, these thrusters cannot operate above an altitude near 100 km. They are therefore not usable at altitudes higher than this, such as for example to allow the transfer of satellites toward higher orbits.
Moreover, document US2008/116808 describes a plasma thruster technology which can be implemented on an outer wall.